1. Field of the Invention
This invention relates to desiccant containers for use in air or fluid dryers of automotive air conditioning systems, and more particularly, it relates to a desiccant container having a mount for a canister tube and an inner wall extension portion which facilitate returning dehydrated air or fluid to the air conditioning system.
2. Description of Related Art
Desiccants are commonly used in automotive air conditioning systems for dehydrating air and refrigerants. Particulate desiccants are common in such systems because the high surface area-to-volume ratios of the particles facilitates the interaction of the particles with surrounding air or fluid. Since the particles of desiccant must be held in the air or fluid stream and prevented from contaminating other parts of the system, the particles must be held in a container which is permeable to the air or fluid but impermeable to the particles.
One form of dryer used in automotive air conditioning systems includes an elongated receiver or accumulator canister having inlet and outlet ports communicating with the interior of the canister. A desiccant container is positioned in the interior of the canister and allows for air and/or fluid through the desiccant material.
One form of package-type desiccant container for use in an accumulator or receiver dryer is constructed from synthetic felted wool or polyester which is filled with desiccant and then sealed by stitching or fusing. One drawback to this form of package is that the felted bag may not conform to the shape of the canister, so that air or fluid may bypass the desiccant. Another drawback is that the bag may be non-uniform in shape, thereby making automatic assembly of the dryer difficult.
If felted polyester is used as a less expensive substitute for felted wool, the seams of the bag may be formed by ultrasonic welding. Unfortunately, the reliability of such ultrasonic welds is questionable and the bag may open up, allowing adsorbent material to escape from the bag and potentially contaminate the system. In addition, the felted polyester bag is vulnerable to burn-through when the dryer is welded shut.
In another proposed form of an accumulator or receiver dryer, particulate desiccant is trapped between a pair of grids or plates which are welded or press fit inside the canister. According to one embodiment, the desiccant is charged by pouring the desiccant particles into the canister once a first of the grids or plates is positioned. A pipe extends through holes in the grids or plates to exhaust dried air to an outlet port.
A dryer of this form is likely to be difficult to assemble because the grids or plates must be slid into position and, in some cases, welded inside the canister. Further, since the desiccant particles are manually poured into the canister, the desiccant must be pre-measured due to the difficulty of controlling the amount of desiccant poured into the canister based on visual observation alone. The pouring of the desiccant creates a risk of accidental contamination outside the accumulator since desiccant particles may fall into the pipe communicating with the outlet port. Nevertheless, the amount of desiccant poured into the canister may vary from canister to canister for at least the reasons mentioned above.
Copending patent application Ser. No. 08/235,283, assigned to the same assignee of the present invention, discloses a two-piece desiccant container which can be inserted within an accumulator or receiver dryer canister. The desiccant container includes a cup for holding particulate desiccant and a removable cap which retains the particulate desiccant within the cup.
The cup includes a tubular inner wall portion, a concentric outer wall portion and a transverse web portion which cooperate to define a chamber for holding the desiccant. The inner wall portion defines a central axially extending sleeve for receiving an aluminum canister tube of the accumulator or receiver dryer canister. In operation, the aluminum canister tube passes completely through the inner wall portion of the cup to return dehydrated air or fluid which has passed through the desiccant to the air conditioning system. A dehydrated air or fluid return path formed solely of aluminum tubing can be an incremental cost drawback.